[ltp] Display unreliable - W500
Thu, 07 Nov 2013 10:43:30 +0600
On 11/07/2013 06:00 AM, Wade Curry wrote:
> So the question is, does this sound like a bad CCFL tube, or does
> it sound like something else? If it's a bad CCFL, is there a good
> tutorial on it? Otherwise, does it even sound reparable? I'm not
> able to pay someone else to do it, but I've got a soldering iron
> and willingness to dig in.
First of all, the required disclaimer. I'm not responsible for anyone's
actions and the damage to equipment and human health or even death
resulting from carelessly applying the following directions. CCFL
backlight units use *LETHAL* 2000 volts to start up and serious 200-400
volts is the working voltage. You have been warned.
Replacing CCFL can be a hard job but you won't know what component to
blame: CCFL or inverter.
Get a 100% alive same-size CCFL (hard to get, easy to test) or get a
good 17" 4:3 LCD monitor for test. 4:3 units are old and usually come
with CCFLs, not LEDs. The length (and thus most electrical parameters)
of your 15" 16:9 CCFL is the same as on a 17" 4:3 screen - it's
important. Don't get anything larger - it doesn't fit for test.
Open a monitor, disconnect everything from the LCD panel. Now you got
the bare panel with (usually four) cables protruding from the side of
it. These cable come to backlight CCFLs - the same as on your thinkpad.
Now rich your bare thinkpad LCD panel - there are plenty of instructions
available online including official manuals from Lenovo.
Disconnect the thinkpad's CCFL from the inverter and manage to connect
one of your test monitor's CCFLs to it. It may involve messing with thin
wires (by pushing them inside the CCFL connector openings and soldering
to thinkpad's inverter).
Now power the thinkpad on and look. If a part of your test monitor
lights up immediately upon powerup (it's ok, only a part - as it takes
more than one CCFL to light the whole screen up) - then it's your
original thinkpad screen CCFL at fault.
Otherwise - it's the inverter.
One more warning for those who still follow reading: playing around with
ripped apart unprotected mains powered electronics without an isolation
transformer is even more dangerous than everything above. You can be
Hey, you can also take inverse test - connect thinkpad's CCFL instead
of one on your test monitor and look. If CCFL is faulty, the monitor
(and your thinkpad screen) would light up for some 2 seconds and then go
dark. Be sure that test monitor receives some picture, otherwise power
saving kicks in and test result is inconclusive.